Dejie Li

Influence of post-deposition annealing on the properties of transparent conductive nanocrystalline ZAO thin films prepared by RF magnetron sputtering with highly conductive ceramic target

Using a highly conductive ZnO (ZnAl2O4) ceramic target, c axis-oriented and oxygen-deficient Al-doped ZnO (ZAO) thin films were prepared on glass sheet substrates by radio frequency (RF) planar magnetron sputtering. The structural, electrical and optical properties of the films (deposited at room temperature and annealed at different conditions) were characterized with various techniques. The experimental results show that the electrical resistivity of as-grown films can be decreased to 10−4 Ω cm level with post-deposition annealing at 400 °C for 2 h in a vacuum pressure of 10−5 torr. By increasing the annealing temperature, the oxygen vacancies and carrier concentration of ZAO thin film increase, and the absorption edge in the transmission spectra shifts toward the shorter wavelength side (blue shift). The oxygen vacancy plays an important role in the electrical conductivity. The more the oxygen vacancies exist in ZAO thin films, the higher the electrical conductivity will be.

Effect of Vacuum Annealing on the Properties of Transparent Conductive AZO Thin Films Prepared by DC Magnetron Sputtering

Using highly conductive Al doped ZnO (AZO) ceramic target, (001)-oriented transparent conductive AZO (Al doped ZnO) thin films are prepared by dc planar magnetron sputtering deposition on glass sheet substrates. The structural, electrical, and optical properties of the films (deposited at room temperature and annealed at different temperatures in vacuum) are characterized with various techniques. The experimental results show that electrical resistivity of the as-grown films (not intentionally heated) can be decreased to 10 -4 Ω cm level with post-deposition annealing at 400 °C for 2 h in vacuum pressure of 10 -5 Torr. AZO thin films deposited at room temperature (RT) and subsequently annealed at 450 °C for 2 h in vacuum have nano-crystalline structure with even crystal size distribution. With the increase of annealing temperature, the (002) preferred orientation of AZO thin film grows, the carrier concentration of AZO thin film increases, and the absorption edge in the transmission spectrum shifts toward the shorter wavelength side (blue shift). The oxygen vacancies have played an important role in the improvement of electrical conductivity of these AZO thin films with the vacuum annealing process.

Vertical aligned carbon nanotubes grown on Au film and reduction of threshold field in field emission

Vertical aligned carbon nanotubes were synthesized on quartz glass and Au film by catalytic decompositon of ferrocene and xylene. Morphological differences between aligned nanotubes grown on the two substrates are studied and discussed through SEM images. Field emission testing shows that aligned nanotubes grown on Au have a lower threshold field than those grown on quartz glass. This reduction of threshold field indicates a new way to improve field emission properties through the selection of a highly conductive growth substrate for carbon nanotubes.

F+ ion implantation induced cell attachment on intraocular lens

Cell attachment on the polymethylmethacrylate (PMMA) intraocular lens (IOL) was studied by ion implantation. F+ ion implantation was performed at an energy of 80 keV with fluences ranging from 5 x 10(12) to 5 x 10(15) ions/cm2 at room temperature. The cell attachment tests gave interesting results in that the number of the platelets, the neutral granulocytes, and the macrophages adhering on the surface of the IOLs was reduced significantly after F+ ion implantation. The optimal fluence was about 3 x 10(14) to 4 x 10(14) ions/cm2. The hydrophobicity imparted to the surface was also monitored. At the same time, no appreciable change in the tensile strength and the optical transmittance of the implanted samples was observed. X-ray photoelectron spectroscopy (XPS) and fourier transfer infrared (FTIR) analysis showed that F+ ion implantation caused the cleavage of some pendants, the oxidation of the surface, and the formation of some new F-containing groups. These results were responsible for the cell attachment changes.

Studies of diamond-like carbon films coated on PMMA by ion beam assisted deposition

Abstract Diamond-like carbon (DLC) films on polymethylmethacrylate (PMMA) substrates were prepared using ion beam assisted deposition. The carbon films deposited by Ar+ sputtering graphite were simultaneously bombarded by CHn+ at the bombarding energies of 200–1000 eV. The morphology, structure, and bonding states of the films were characterized by Scanning electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, and UV–visible absorption spectroscopy respectively. Results showed that DLC films were amorphous and smooth with higher fraction of sp3 bonds in the structure of mixed sp3+sp2 bonding. The friction coefficient of the DLC/PMMA system was examined.

Magnetron sputtered AZO thin films on commercial ITO glass for application of a very low resistance transparent electrode

In this paper, we report a coating method of reducing the sheet resistance of commercial Sn-doped In2O3 (ITO) glass by DC magnetron sputtering, without reducing its optical transmittance in the visible range of spectra. Aluminium oxide doped zinc oxide (AZO) films deposited on ITO glass showed highly (002)-oriented textured structure. An experimental procedure was designed to minimize the sheet resistance of AZO/ITO films in the deposition parameter space (mainly deposition temperature). Resistivity measurements showed that the ITO films with AZO coated under optimized deposition conditions showed a significant 81.4% decrease of sheet resistance when compared with those formed without AZO. Room temperature Hall effect measurements showed that the Hall mobility of the combined layers was greatly increased compared with that for single layer ITO. A high quality transparent electrode, having a resistance as low as 4.13 Ω/square and a high optical transmittance of 80% in the visible spectral range (with substrate), was obtained. The bilayer AZO/ITO film glass may be a good alternative substrate to ITO glass for advanced electro-optic applications.

Electron emission from discontinuous gold-carbon compound film on etched porous aluminum oxide

An electron emitter composed of discontinuous gold-carbon compound conducting film on etched porous aluminum oxide (PAO) layer is proposed in this letter. The PAO layer is located between two 30μm spaced cathode and grid electrode, and is etched in diluted phosphoric acid to introduce roughness on the soda lime glass surface and enhance discontinuity of the conducting film. Electron emission with good uniformity and stability is reproducibly obtained. The electron emission efficiency is higher than 2% at an anode voltage of 3kV.

A light-trapping structure based on Bi 2 O 3 nano-islands with highly crystallized sputtered silicon for thin-film solar cells

Silicon films with light-trapping structures are fabricated based on Bi2O3 nano-islands, which are obtained by annealing Bi nano-islands in the air at 400 °C. The topography exhibits the maximum altitude of over 600 nm and the root-mean-square roughness of 150 nm, with the lateral size of single island of about 1 μm. Highly crystallized sputtered silicon, realized by Cu-induced crystallization, is used to be a light-absorbing layer. Reflectivity of the samples with different thickness of silicon has been studied to reveal the light-trapping efficiency. The average reflectivity under AM1.5 illumination spectrum is 12% when silicon is 480 nm thick and the reflectivity for the long wavelength region between 800 nm and 1100 nm is less than 10% when the silicon is 1.2 μm thick. This is a promising low-cost structure for crystallized silicon thin-film solar cells with high efficiency.

Ion-beam-induced biomedical behavior of hexamethyldisiloxane films on deposited polyetherurethanes

Abstract The influence of silicon ion implantation on hexamethyldisiloxane (HMDS) layers deposited on polyetherurethane (PEU) films was investigated. HMDS deposition onto PEU was performed using plasma chemical vapour deposition for a deposition time of 5 min, and then Si+ ions were implanted into the HMDS layer at an energy of 80 keV with the dose ranging from 2×1013 to 2×1016 ions/cm2 at room temperature. Studies of biomedical behavior indicated that the coagulation time was about three times greater after HMDS deposition and then Si+ implantation with 2×1015 ions/cm2 relative to the pristine sample. At the same time, the anticalcific behavior and the wettability were also enhanced significantly after the surface treatment. X-ray photoelectron spectroscopy and electron spin resonance analysis demonstrated that ion implantation not only broke some chemical bonds on the surface, but also formed some new higher polar Si-containing groups and new radicals, which was probably the main reason for the surface modification.

Ion beam-assisted deposition of DLC films on PMMA and TiN/PMMA

Abstract Bilayered films composed of diamond-like carbon (DLC) and titanium nitride (TiN) or individual DLC films were prepared on the surface of polymethylmethacrylate (PMMA) substrates using ion beam-assisted deposition. The deposition of the DLC or the TiN films were carried out by Ar + sputtering graphite or titanium targets and CH n + or N + ion beams simultaneously bombarding the resulting films at various energies. Results of scanning electron microscopy, X-ray photoelectron and Raman spectroscopy analysis indicated that the DLC films on the PMMA and the TiN/PMMA substrates were amorphous and smooth with the structure of mixed sp 2 +sp 3 bonding. The DLC films on the TiN/PMMA system exhibited an obvious improvement in hardness and wear resistance as comparing to the PMMA only substrate.